Generally speaking, the pitch in the paper manufacturing process means a sticky resin component contained in a raw wooden material and a sticky synthetic substance contained in a recycled used paper, and also a hydrophobic sticky substance mainly comprising an organic substance derived from an added chemical used in the paper manufacturing process.
In the pulp manufacturing process to manufacture a pulp from a pulp raw material and in the paper making process to manufacture a paper from a pulp, at odd times there appear troubles due to the pitch. Namely, although the pitch is present in water as a colloid, when this colloidal state is damaged by a large shear force, by changes of pH and water temperature, by addition of a chemical, or the like, this pitch is separated out in water or on a paper-making equipment, or when agglomerates of fine pitches themselves which are separated out in water attach on a paper-making equipment, at odd times these may cause contamination of a product with the pitch agglomerates, poor squeeze out of water, breakage of a paper, and so forth. Because of these, there appear problems such as decrease in the product quality as well as decrease in the productivity because the equipment for paper making and so forth needs to be cleaned by stopping it.
The troubles due to the pitch appear readily, especially when a deinked pulp and a raw material of a used paper including a used carton box, as well as a broke raw material which reuses a waste paper, are used.
In recent years, the ratio of the used paper brought into a raw material is increasing and the unit consumption of industrial water is decreasing; and in proportion to these trends the amount of the pitch which is brought into the paper manufacturing process increases; and thus, not only the troubles due to the pitch is increasing but also they are becoming more complex.
To suppress the troubles due to the pitch, various methods have been proposed.
In Patent Document 1, it is described that a specific coagulating agent (a polymer which contains diallyl dimethyl ammonium chloride) is used to prevent the pitch from separating out.
In Patent Document 2, it is described that the pitch is suppressed by using a flocculant.
In Patent Document 3, it is described that the pitch is adsorbed to a talc.
In Patent Document 4, it is described a pitch anti-fouling agent for paper making which comprises a nonionic surfactant and a polymer comprising, as composition units, maleic acid or maleamidic acid, as well as isobutylene, diisobutylene, or styrene.
In Patent Document 5, it is described that the pitch is decomposed by an enzyme which is derived from a specific microorganism.